RE: [Dev-C++] [Dev-C++]: Errors in structures

[Lover of C++ <lo...@gl...>]

It is not a bug, it is compiler feature. For some optimizations some c++
compilers adjust the size of structue to the multiple of 8.


Hi there
-------------
I am sorry to say that I dont have an answer for you . The LibC help file
does say that the Data Types can vary from Compiler
to Compiler But I WOULD like to show what I have also picked up with your
Code

//Snippet - START
#include <iostream.h>
#include <stdlib.h>
#include <limits.h>

struct tea_hdr{
  int version; //-- 1
  char jte[3]; //  -- 2
  //char fname_sz; // -- 3
  //char infile_size; // -- 4
// char infile_crc; // -- 5

  }header;


int main()
{
       cout<<"Char Minimum : "<<CHAR_MIN<<endl;
       cout<<"Char Max : "<<CHAR_MAX<<endl;
       cout<<"Unsigned Char Max : "<<UCHAR_MAX<<endl;
       cout <<"Header : "<<sizeof(header)<<endl;
       cout<<"Struct : "<<sizeof(tea_hdr)<<endl;
       system("PAUSE");
       return 0;
}

//Snippet END

Now if you compile it as follow the Size of the Structure is 8 (The integer
(5) and the char[3]) That is ok.,

Now remove the comment before item 3 and compile and run Again.. The size
is STILL the same ?? Is this just my
PC.. must I reboot.. BUT there is more.

Now uncomment item 4 .. Compile and RUN.. SIZE is 12 that is 4 bytes
extra,But there is still more

Now uncomment item 5 and compile and run.. IT stays at 12 bytes again..
This seems to be variable
items count related. I have sifted the vars around and nothing is with
there posisions..
Also it only starts when MIXING variables in the structure.. I have a
feeling that this is something
that can be compiler related.. BUT what I did notice in the 'stddef.h' File
is that the MingW32 oaks have
a prob with the defs of the Gcc compiler and has added some macro to fix it
.. I wonder if maybe something else
also was missed that can relate to this. That the problem can maybe be at
the MingW32 project.

I don't have any answer's just maybes. but maybe it can help you in getting
to a answer For IF I cam correct you are trying to
read the information into the structure from a File .. like the header of a
MP3..

I dont have any other Ideas atound this but I hope you get a solution

Good luck

Johannes






At 09:22 03/07/2001 +0530, you wrote:
>Hi,
>
>I've noticed this strange little Bug.I'm not certain weather its a bug or a
>feature.
>
>The size of this structure is actually 13 bytes.
>
>But sizeof(header) says its 16.
>
>struct tea_hdr
>  {
>  char jte[3];
>  unsigned char version;
>  DWORD infile_size;
>  DWORD infile_crc;
>  unsigned char fname_sz;
>  }header;
>
>No, if I comment out the fname_sz member,
>
>struct tea_hdr
>  {
>  char jte[3];
>  unsigned char version;
>  DWORD infile_size;
>  DWORD infile_crc;
>  //unsigned char fname_sz;
>  }header;
>
>sizeof(header) returns 12.
>
>Is the compiler trying to align structure on DWORD boundaries?
>
>How do I get rid of this Bug/Feature ?
>
>Thnx,
>Jeethu Rao
>
>
>_______________________________________________
>Dev-cpp-users mailing list
>Dev...@li...
>http://lists.sourceforge.net/lists/listinfo/dev-cpp-users


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